textproduct: Albany

WHAT HAS CHANGED

Some adjustments to hourly PoPs for the showers this afternoon into tonight with the continued slightly further northward track of the low pressure system across PA/MD towards NJ. A Marginal Risk (Level 1 of 4) from WPC continues for locally heavy rainfall or an isolated flash flood risk across southern Ulster, Dutchess and Litchfield towards I-84. QPF was used from WPC for the forecast this afternoon into tonight with a half an inch to an inch basin average expected with some locally higher amounts in NW CT.

PoPs were reduced to slight chance (15-20%) Saturday afternoon mainly from the Capital Region north and west before chances increase Saturday night.

KEY MESSAGES

1) Moderate to heavy showers may produce ponding of water on roadways, poor drainage flooding or an isolated flash flood along and north of I-84 in southern Ulster, Dutchess and Litchfield Counties this afternoon into tonight.

2) Additional rounds of showers with isolated to scattered t-storms this weekend due to multiple disturbances associated with an upper level trough. Locally heavy rainfall or isolated flash flooding may occur in locations that see repeated, moderate to heavy rainfall rates especially well southeast of the Capital Region.

DISCUSSION

KEY MESSAGE 1...

A cold front remains across eastern New England and NJ this afternoon. A low pressure system is moving across the PA-MD border. Low and mid level warm advection is increasing across northeast PA into central-eastern NY with developing showers with support from the right entrance region of an upper level jet streak over upstate NY. The best low to mid level FGEN in the H850-700 layer is south and east of the Capital Region this afternoon into early tonight. PWATs have risen into the 1.3-1.7" range from the Greater Capital Region south to the I-84 corridor in southern Ulster, Dutchess and Litchfield Counties. PoPs were increased into the slight to chance range as far north as the Mohawk River Valley, southern reaches of the Lake George Saratoga Region and southern VT. The highest PoPs in the 55-80% range continue to be across the eastern Catskills, mid Hudson Valley, southern Taconics, southern Berkshires and Litchfield Counties, where the better forcing overlaps with the moisture convergence.

WPC continues a Marginal Risk (Level 1 of 4)in th Day 1 ERO for the locations just north of I-84 in southern Ulster, Dutchess and Litchfield Counties for isolated instance of flash flooding. The gridded 1-hr FFG remains high in these areas in the 1.8-2.5" range, and the 3-hr values are generally 2.5-3". The latest HREFs shows rates of 0.1-0.25"/hr into tonight with briefly higher amounts of 0.25-0.50"/hr. The high FFG values and the rainfall rates not too high is why we held issuing a Flood Watch. Some poor drainage flooding of low-lying and urban areas may occur. We kept thunder out of the forecast with very little instability of less than 300 J/kg south and east of Albany in the HREF. We also used the WPC QPF with basin average amounts of 0.50-1.00" over the mid Hudson Valley, eastern Catskills, southern Taconics and Litchfield, CT. Localized amounts of 1-2" may occur if any higher rainfall amounts occur or training. Expect higher amounts further north of a tenth to a quarter inch to the Capital Region and southern VT and a trace to a few hundredths of an inch. The showers should end quickly from northwest to southeast shortly before or just after midnight. The skies will become mostly clear to partly cloudy, especially northwest of the mid Hudson Valley/NW CT with some patchy to areas of fog developing in the valleys. Lows fall back into the 50s with some 40 over the southwest Adirondacks.

KEY MESSAGE 2...

High pressure builds in from southern Quebec with a mainly a dry day across eastern NY and western New England with dewpoints in the 50s to lower 60s, so humidity levels will be comfortable. Max temps will be seasonal in the 70s to lower 80s with a few upper 60s over the higher terrain. A mid and upper level trough begins to dig in Fri night from south of James Bay across the Great Lakes Region/Ohio Valley. A southern stream short-wave moves northeast of the TN Valley into the mid-Atlantic Region Sat morning along the eastern periphery of the deepening trough. Clouds increase with the greatest probabilities for showers and a few thunderstorms south and east of the Capital Region during the afternoon into the evening. We lowered PoPs to the 15-20% range from Albany north and west Saturday until the next short-wave approaches from the south and west for Sat night into Sunday. The ensembles and short-range guidance shows some spread with the timing of these features. WPC continues a Marginal Risk (Level 1 of 4) in the Day 3 ERO for southeast Dutchess, Litchfield Counties. If showers or thunderstorms repeatedly move over the same area with excessive rainfall rates and with wetter antecedent conditions, then an isolated flash flood can not be ruled out. Temps will tend to run slightly cooler than normal on Sat with mid 60 to lower 70s over the higher terrain and mid and upper 70s in the valleys.

The broad, mid and upper level trough shifts from a neutral tilt to negative tilt over NY and New England with the closed H500 low south of James Bay. A low pressure system and a sfc trough or occluded front will bring periods of showers and a few thunderstorms on Sunday. PoPs continues continue in the 70 to 95% range. The NBM 24-hr Probs for >0.50" of rainfall by 00Z/Mon are in the 30-50% range across eastern NY and western New England with highest Probs over the Mohawk Valley and southwest Dacks. The rainfall should be mainly beneficial, as the previous discussion noted. Temps continue to run near or slightly below normal to close the weekend and open next week. The upper level low begins to move away Mon into Tue with lingering cyclonic flow and upslope/instability showers over the higher terrain with seasonal temps for late AUG.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

Area of steady light rain continues to impact southeastern areas this evening and will continue for the next few hours. Flying conditions have been IFR at KPOU due to visibility as low as 2SM in moderate rainfall. Meanwhile, the rest of the TAF sites remain VFR, even at KPSF where a steady light rain has been occurring. Over the next few hours, rainfall will be tapering off, so will continue a brief TEMPO at KPOU for IFR visibility and will include a TEMPO at KPSF for MVFR visibility as well, but the trend will be for rain to taper off in the next 1 to 3 hours. Once rainfall ends, clouds will also be starting to clear out from west to east. With the clearing occurring first at KGFL, good radiational cooling conditions there could allow for a brief period of fog just prior to daybreak, so will include a TEMPO there for some mist/fog right around sunrise. Elsewhere, it will remain VFR, with bkn-ovc mid level clouds becoming few- sct by the late night hours. Winds will remain light to calm through the overnight hours.

On Friday, flying conditions will be VFR for all sites with no precipitation expected. Just some sct cumulus around 4-6 kft is expected for all sites during the late morning and afternoon hours. Northeast winds will be 5 to 10 kts during the day on Friday.

Outlook...

Friday Night: No Operational Impact. NO SIG WX. Saturday: Low Operational Impact. Slight Chance of SHRA. Saturday Night: Moderate Operational Impact. Chance of SHRA. Sunday: High Operational Impact. Definite SHRA...TSRA. Sunday Night: Low Operational Impact. Slight Chance of SHRA. Monday: Moderate Operational Impact. Chance of SHRA...TSRA. Monday Night: No Operational Impact. NO SIG WX. Tuesday: Low Operational Impact. Slight Chance of SHRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.